The grammar rules of the modal and auxiliary verbs vedere (see), volere (want) and avere (have) in modern Italian reveal a cognitive scheme underlying the superficial linguistic structure that depends on a certain conceptualization of reality within the Western world cultural models. The article therefore puts forward a semantic approach to grammatical rules based on these conceptual and cultural motivations. The principles of structural European semiology, as introduced by Saussure, form the basis of the paper; particularly the understanding of signs as double entities (signifier/signified) whose arbitrary connections are assured by a system of sociocultural values, so that the cultural value of historical linguistic association impacts upon grammatical rules, meaning and social understanding. Grammar enables the actualization of certain semantic meanings amidst the plurality of virtual values contained within a certain syntactic combination of units. The inclusion of certain values within a given discursive isotopy supports a mode of signification, but it does not annul the possibility of the others that might be anchored in alternative discursive isotopies. In other words, there is distinction between the function of a sign in a system (langue) and the function that the same sign possesses in the concrete act of its usage (parole). Thus, this paper revises Saussure’s semiological model from a cognitive perspective, placing particular emphasis on the question of cultural values.